This job took two people one afternoon. We got muddy because we were in a dirt crawlspace doing just that, crawling. We used 18,000-pound screw jacks, 4×4 lumber, a circular saw, power drill/driver, and cement blocks. Total cost was less than $200, while a pro would charge $500-$1000.

The Story:

This past Saturday, my brother had me over to help move some of his furniture during the annual rearranging of the tv room. The photo below shows what we saw when we moved the couch away from the wall.

Look for the 1 inch gap between the floor and the base board

Apparently, it’s been that way since they bought their 90-year-old bungalow and it’s been nagging at my brother ever since. You may have similar areas in your home. You probably feel the same way my brother did: “it’s not THAT big a deal and it’ll cost at least $1000 to repair, so let’s buy diapers and food and gas with our money instead.” Well, it isn’t THAT big a deal now, but it could develop into a whole host of problems down the line, especially if the sagging is caused by a larger issue.

Three 18000 lb screw jacks and solid concrete blocks for support

The truth is, it will cost you upwards of a thousand dollars to hire professionals to do anything to your foundation or the under-structure of your home. Just plan on that. Plus, it’s hard to find the right people to do this work, because it requires on-site problem solving and a certain amount of risk assessment (don’t hire anyone that seems kind of stupid). I know this. We paid to have some work done on our sill plate last summer and it hurt the wallet. A lot. However, watching the crew work on my house let me know that I could certainly do that work myself the next time the need arose.

We ripped the 2×10’s in half to make four 4 ft joists

As a homeowner with an eye for and interest in how things work, I’ve learned an extremely important thing: my house is actually really simply built and nothing in here is all that complex. The trouble is knowing what to do and what tools to buy. If you aren’t good at figuring stuff out on your own, hire someone. . . once. While they’re working, ask them questions about the process and about what they’re doing. Assess whether you think you can do it yourself. I learned most of my skills out of necessity (it’s a cash flow thing) and by watching professionals.

As with many old houses, my brother’s has a tiny crawl space door. I’m large so that makes me unhappy.

For this job, as with any job, we first needed to figure out what the root problem was. The sagging floor was the symptom, and somewhere under the house there had to be a cause. Well, after doing the navy SEAL crawl up under the house, we found that the joists that were supporting that floor were not actually attached to the sill plate any longer, as seen in the photograph below. This is an obvious problem, considering the fact that the sill plate is the first line of support above the foundation wall. You can see that the joist had dropped about an inch below the sill, explaining the inch the floors had sunk.

The joist had slipped about an inch from the sill

In order to lift this section of flooring back up an inch, we needed to purchase a few screw jacks, which can be purchased at your local big box hardware store for about $30 per jack. The ones in the photos above are actually not the ones we ended up using. We had to buy shorter ones. But hey, what’s a home improvement project without at least two trips to the store?

Moving around under old houses can be tricky. My brother’s crawlspace opens up quite a bit once you’re inside. It used to be a dry cellar for storing produce during the summer, with a trap door in the kitchen.

As you can see in that last photo, my brother’s crawl space is rather spacious in spots. Unluckily for us, the spot we were working wasn’t one of the spacious ones. Here he is squeezing through the little trap door. Note the coveralls. I’d recommend covering yourself when working under the house. It’s nasty and there are spiders and junk.

A gift my brother and I both possess: flashing a goofy smile at a moment’s notice.

Here’s where we were working. The 2″x8″ joists you see in the photo (the boards running from left to right above my brother for the lay men) are the ones we would be supporting. We decided that we wanted to sister a new 2″x10″ board up against the existing joists and support the new joists. We chose this method because of the small amount of old termite damage we saw in some of the old joists. What we did was lay the new board flush with the floor boards and with the old joist. We then fastened the two boards together with 3 inch wood screws.

The crawlspace was really tight in the area we were working. Luckily, it was pretty dry. The vapor barrier and outside drainage had done their job well.

Below, you can see my brother prepping one of the new joists by partially driving the screws into the wood. This is surprisingly difficult to do when holding a twenty pound joist and a drill above your head while lying on your back.

I used to balk at the drills and power tools that come with a light. Not any more. That little light came in very handy.

With the mud and the muck, I didn’t get any photos of the next step or two. In the photo below, you see the final product. You can see how the new joists are attached and, if you look towards the background, how they overhang the old joists so the support beam is only pushing on the new joists.

Here’s the completed job. The new joists are attached to the old joists and are supported by the 4×4’s and screw jacks.

Once the new joists were up, we found locations where the concrete blocks could sit flat on the ground so the pressure wouldn’t cause them to crack. After they were in place, we hoisted up the 4″x6″x8′ beam so that it crossed all four of the new joists, sliding the screw jacks underneath. With the beam resting nicely on the jacks, we slowly turned the red handles until the beam was in contact with two of the joists. Then we kept turning until it was in contact with all four of the joists (the lower two lifted up to be in line with the higher two). By yelling through the floor to my brother’s wife, we were able to coordinate our slow turning of the screw jacks until the crack between the floor and the base board was gone.

Here’s the final product. Total, this job cost my brother $150-$200, where a pro would easily have charged $800-$1000. I’ll admit, this is probably not the job for a first time do-it-yourselfer, but folks with a little experience and confidence can easily repair the sagging floors in their homes.

Look for the 1-inch gap between the floor and baseboard. It’s not there any more.

Thanks to “The Bennetts”. I have a log burner and stone hearth and there is an emerging gap between the architrave and the boards, and worse, the chimney attachment to the top of the burner has nearly popped out because of the quarter inch drop. I am in Australia, so my screw jacks are about three times the price, but I will be tackling my problem in the same manner this weekend. Thanks heaps.

So the floor jacks stay permanently under the house from that point on then? My wife and I are looking at buying an old house and sagging floors is one thing I’ve noticed on the edge of the ground floor rooms.

I’ve got jacks under every room of my house. Most of them were there when we bought the place. When old wooden homes were built, the floors were not supported as much as they should have been for 100+ years of use. I guess they just didn’t expect the house to hang around that long.

You don’t have to leave them under there permanently, what we’ve done in the past is you use two regular jacks with blocks instead of the floor jacks, then put in a stack of cinder blocks (with the flat blocks or a dug and poured concrete pier beneath them) and then a couple wooden blocks on top (they’re needed to get the height right as well as to help spread out the force so that you don’t crack a block)

I’m about to start a similar project… but I read you should dig a hole and put cement on it to build a strong footing rather than using a cap concrete block… Wouldnt your cement blocks sink over time due to the weight of the house pushing down?

I agree it is probably better to dig the hole and pour cement if you’re lifting the house a lot or if you’re only using a single jack. I think we’re fine since we used multiple jacks and we were really just redistributing the weight.

If they sink, we can go back and tighten them up, or pour a pad like you suggested. Thanks for reading.

This response just saved me a ton of time and effort. I was going to fill several holes with concrete, then wait for it to set, etc… Never thought about the fact that I could simply re-adjust the jacks every year or so! Thanks for doing the thinking for me.

It might. I’d suggest looking at the joists under your floor and then get into the attic and check the roof structure, looking for sagging or other abnormalities. If the floor is sagging, bit there is no noticeable snagging in the roof, it could just be the floor. If unsure, have a pro come out and inspect it and give you pointers. You may pay a few hundred bucks on the inspection, but they might convince you that you can do the job yourself. Good luck.

The screw jacks used shown in your pictures seem a different brand product, not the Akron ones shown in your second image — I bought the Akron screw jack, it won’t turn higher due the screw base will turn also. What is the brand of the screw jack you finally used?

I googled Akron screw jacks and what I found seems very similar to the Tapco brand jacks shown in these photos. I think that either brand will work, so long as you purchase the correct height. During one of our trips to the hardware store, they only had one size, so be sure to measure the height of your space and buy jacks that fit within that range. I can’t say for sure, but I think your jacks are too short for your space.

Maybe the early made was with turning bar insert through a hole as shown in your image. I bought the adjustable floor jack 2 ft 10 – 4 ft 7 height, multiple pieces to assemble. And I also looked at the shorter ones, not like what you showed here. Tapco brand is sold in Home Depot, very similar to Akron brand which is sold in Lowes, but they do not look like the ones shown in your images.
I googled and found Ellis brand heavy duty steel shore jacks look more like it. But they are out of stock for the size I want.

Thanks for reading, Penny. Good luck on the repairs. If it gets too crazy down there, don’t be afraid to call a pro for a consult. They can always give advice on what they’d do, even if you don’t hire them to complete the work. They might charge fifty bucks for the visit, but sometimes that’s worth the advice.

Wow! That is a lot of sag. Obviously the beam is undersized, for that to have been installed like that shows inadequate knowledge of safe building practices. You need to get an overall assessment of foundation and support structure from a professional, urgently.

What’s your thoughts on an older A frame cabin, that drastically needs to be leveled due to the ground being sand and no foundation, just sitting on cinder blocks (for around 40 years)?? Warped floor joists, of course! My husband (the know it all handy man) wants to tackle this one on his own, I do not doubt his skill however, I am afraid of more permanent damage being done to the structure if something goes wrong.. PLEASE need your thoughts/input!! Thanks!!!!

My mother’s ranch style house also is built in an area with a lot of sand. Her support beam has a crack all the way through, likely due to water damage and stress. Will concrete footers need to be poured – how far down should they be set? Did you need a permit in your area for this job? Is a wood beam under the house better than an I-beam?

Those are really great questions, but I’m not sure I have answers for you. I do know that if you suspect water damage is the cause, you need to make certain that the leak is fixed before you repair the damage. As for the beams and footings, I recommend you have a few pros come out and assess the structure. That’s what I’ve done in my crawlspace. Most will come for free and will be honest with you. If what they describe seems simple enough, do it yourself. If not, hire someone. The job described in this post was pretty simple, so we had no trouble doing it ourselves.

ANY SUGGESTIONS ABOUT DIGGING PIER HOLES , I HAVE HEARD THAT DIGGING A 18 INCH HOLE AND PACKING BASE MARTIAL IN IT IS BETTER THAN CONCRETE , BECAUSE THE WEIGHTED CONCRETE WILL SINK , WHAT ARE YOUR THOUGHTS ?

How do you figure out what size of jack you need? I’m looking to raise my sagging wooden floors and the height of my basement is 7 feet. I’m just unsure of how much my house weighs and I don’t know how much weight I need the jack to hold. Is there anyway to calculate it?

That’s a great question, Kristan. I actually don’t know how to calculate the weight of a home. I bought heavy duty jacks and assumed that they wouldn’t be fully supporting the house. Remember, your home already has support, so you’re not supporting all of the weight. You are simply adding support where there is a lack.

However, if you are still concerned, you can ask a structural engineer in your area to estimate the home’s weight and make a recommendation on jack type.

The house you where repairing was built using balloon construction,The exterior walls sit directly on the foundation wall and the floors float.That is why only the floor dropped instead of the entire structure.You were lifting just the weight of the floor.Most ranches and two stories built in the fifties and after were built using platform construction where walls sit on top of the floor joist that sit on foundation wall. In this style framing the entire structure will sag in that area usually causing cracks in walls,ceilings or doors rubbing their frame.You will need a proper footing under the post jack because your lifting much more weight.If your correcting a sagging interior floor in ether style framing locate the main support beam in that area [the large beam that the floor joist are sitting on] raise that area.Keep in mind if its drastic have the foundation evaluated.

the house we just purchased as a crawl space. The foundation is stone and needs some repair. The main load beam is cracking. The joists have been notched out a lot to sit over the main beam.
Deep enough that there is only about 4″ difference in height between the beam and joists (Obviously this weakens the joist).
It looks like the outside walls rest on the stone foundation.

My thought is to first sister the main load beam with 2 x 10 boards then support it with several jacks. Next sister the joists for more strength.
My question is: would I use joist brackets to attach the joists to the new main load beam.
Basicly it would be like building a deck.
The new joists cannot sit on top of the beam without raising the whole house.

We intend to do this after removing the floor boards and working from above and below.

Another technique is to purchase ready made pier blocks 12″x12″ ($3 each) with the small hole predrilled for simpson 4×4 adjustable post supports.($10 each) This allows you to attach any 4x material with nails or screws and the simpson post support which then can be jacked up like a screw jack up to 2.5″. I used this technique to support a similar issue in my house.

Hi, there. When you talk about hiring “pros,” what would this be a structural engineer, basement company, etc.? We’re experiencing significant floor sagging around the edges of the house, and I’m at somewhat of a loss of whom to call, as we live in a small town. (We have the added misfortune of having a super small crawlspace height-wise, so jacking things up will likely require some removal of floors.) Thanks for any ideas of the best types of companies to call.

I know this article is from years back, but from a leveling perspective, I guess you just eyeballed it? Technically, it’s not an old house (1989), but the builder built it wrong, and there has always been a hump in the floor of the kitchen (and what might be a sag where the refrigerator is). These appear to be related to the original footings and support – the floor is just not level.

Back when hi-end flooring was vinyl, you could get away with this. 21 years later, I want tile in the kitchen or possible hardwood, so the hump has to be resolved. Ant recommendations for measuring this unevenness?

we need to re support our floor with floor jacks and sistering.It is over a very small or low crawl space.would it be O.K. to take out the whole sub floor to do this work. Our house was built in 1860 in Indiana.

Very interesting article. Was great to see how this is done. My situation involves an upper unit with a pretty steep deflection (up to 1 inch over 4 feet in one place). There is obviously no crawlspace underneath my floor because there is a condo unit (first floor) there. I plan to hire a structural engineer and pay for his expertise/report, but my reluctance is based on how little he will be able to see/evaluate being there is no foundation directly below me, no crawlspace, and no way for him to view joists, etc. Would he need to remove a wall or remove my wood floor? Any idea?

Those engineers are able to see signs and read clues in your structure that you and I cannot see. Have one out to your place and see what they think. They might need to pull up the floor, but probably not.

Things like this make the Internet so priceless. Thanks so much for all the work it took to document this! Buying a house is expensive enough. Maintaining it as a DIY man is necessary for me (it’s a cash flow thing). Your effort is so encouraging to people who don’t have a couple of grand to spare.

Great post, and great pictures! I have a house with a similar looking crawl space and similar floor construction – maybe because my home is of a similar age in Atlanta 🙂 Were you able to get the original joists back on the ledger, or did you just let the sistered joist take the load? I ask because some of my joists are doing the same thing.

Looking back on this project, do you think there is any benefit to jacking up the beam to a correct elevation, and THEN installing sister beams? (vs installing sister beams and then lifting). Not meant to as criticism, but as advice).